Hexagonal Boron Nitride as an Enhanced Anti-Sticking Transmission Oil Additive

ABSTRACT

Disclosed are additive compositions for transmission oils comprising an oil dispersion of a hexagonal boron nitride and a polymethacrylate, a dispersant polymethacrylate or a dispersant olefin copolymer viscosity index improver, as well as lubricating oil compositions containing the same.

The present invention is directed to an additive composition for atransmission oil. More particularly, the present invention is directedto an additive composition comprising an oil dispersion of hexagonalboron nitride and a viscosity index improver, in particular, an additivecomposition containing a viscosity index improver selected from apolymethacrylate, a dispersant polymethacrylate or a dispersant olefincopolymer.

REFERENCES

The following references are cited in this application as superscriptnumbers:

-   ¹ Peeler, U.S. Pat. No. 3,313,727, Alkali Metal Borate E.P.    Lubricants, issued Apr. 11, 1967-   ² Adams, U.S. Pat. No. 3,912,643, Lubricant Containing Neutralized    Alkali Metal Borates, issued Oct. 14, 1975-   ³ Sims, U.S. Pat. No. 3,819,521, Lubricant Containing Dispersed    Borate and a Polyol, issued Jun. 25, 1974-   ⁴ Adams, U.S. Pat. No. 3,853,772, Lubricant Containing Alkali Metal    Borate Dispersed with a Mixture of Dispersants, issued Dec. 10, 1974-   ⁵ Adams, U.S. Pat. No. 3,997,454, Lubricant Containing Potassium    Borate, issued Dec. 14, 1976-   ⁶ Adams, U.S. Pat. No. 4,089,790, Synergistic Combinations of    Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide    Antioxidants, issued May 16, 1978-   ⁷ Adams, U.S. Pat. No. 4,163,729, Synergistic Combinations of    Hydrated Potassium Borate, Antiwear Agents, and Organic Sulfide    Antioxidants, issued Aug. 7, 1979-   ⁸ Frost, U.S. Pat. No. 4,263,155, Lubricant Composition Containing    an Alkali Metal Borate and Stabilizing Oil-Soluble Acid, issued Apr.    21, 1981-   ⁹ Frost, U.S. Pat. No. 4,401,580, Lubricant Composition Containing    an Alkali Metal Borate and an Ester-Polyol Compound, issued Aug. 30,    1983-   ¹⁰ Frost, U.S. Pat. No. 4,472,288, Lubricant Composition Containing    an Alkali Metal Borate and an Oil-Soluble Amine Salt of a Phosphorus    Compound, issued Sep. 18, 1984-   ¹¹ Clark, U.S. Pat. No. 4,534,873, Automotive Friction Reducing    Composition, issued Aug. 13, 1985-   ¹² Brewster, U.S. Pat. No. 3,489,619, Heat Transfer and Quench Oil,    issued Jan. 13, 1970.-   ¹³ Salentine, U.S. Pat. No. 4,717,490, Synergistic Combination of    Alkali Metal Borates, Sulfur Compounds, Phosphites and Neutralized    Phosphate, issued Jan. 5, 1988

All of the above patents are herein incorporated by reference in theirentirety to the same extent as if each individual patent wasspecifically and individually indicated to be incorporated by referencein its entirety.

BACKGROUND OF THE INVENTION

High load conditions often occur in gear sets such as those used inautomobile transmissions and differentials, pneumatic tools, gascompressors, centrifuges, high-pressure hydraulic systems, metal workingand similar devices, as well as in many types of bearings. When employedin such environments, it is conventional to add an extreme-pressure(E.P.) agent to the lubricant composition and, in this regard, alkalimetal borates are well known extreme-pressure agents for suchcompositions.^(1-11, 13) E.P. agents are added to lubricants to preventdestructive metal-to-metal contact in the lubrication of movingsurfaces. While under normal conditions termed “hydrodynamic”, a film oflubricant is maintained between the relatively moving surfaces governedby lubricant parameters, and principally viscosity. However, when loadis increased, clearance between the surface's is reduced, or when speedsof moving surfaces are such that the film of oil cannot be maintained,the condition of “boundary lubrication” is reached; governed largely bythe parameters of the contacting surfaces. At still more severeconditions, significant destructive contact manifests itself in variousforms such as wear and metal fatigue as measured by ridging and pitting.It is the role of E.P. additives to prevent this from happening. For themost part, E.P. agents have been oil soluble or easily dispersed as astable dispersion in the oil, and largely have been organic compoundschemically reacted to contain sulfur, halogen (principally chlorine),phosphorous, carboxyl, or carboxylate salt groups which react with themetal surface under boundary lubrication conditions. Stable dispersionsof hydrated alkali metal borates have also been found to be effective asE.P. agents.

Moreover, because hydrated alkali metal borates are insoluble inlubricant oil media, it is necessary to incorporate the borate as adispersion in the oil and homogenous dispersions are particularlydesirable. The degree of formation of a homogenous dispersion can becorrelated to the turbidity of the oil after addition of the hydratedalkali metal borate with higher turbidity correlating to less homogenousdispersions. In order to facilitate formation of such a homogenousdispersion, it is conventional to include a dispersant in suchcompositions. Examples of dispersants include lipophilic surface-activeagents such as alkenyl succinimides or other nitrogen containingdispersants as well as alkenyl succinates.^(1-4, 12) It is alsoconventional to employ the alkali metal borate at particle sizes of lessthan 1 micron in order to facilitate the formation of the homogenousdispersion.¹¹

In addition, anti-sticking agents are often employed in automotive gearboxes to provide smooth synchronization and good shift ability. Examplesof such anti-sticking agents include phosphates, phosphites,phosphonates, thiophosphates, carbamates, molybdenum dithiocarbamatesand dithiophosphates.

It is also known that boron nitride exhibits friction modifyingproperties in lubricants. For example, U.S. Pat. No. 4,787,993, issuedNov. 29, 1988 to Nagahiro, discloses a lubricant effective for thereduction of friction which comprises dispersing a finely powderedaromatic or polyamide resin into a fluid fat or oil, which mayadditionally contain molybdenum disulfide, organic molybdenum or boronnitride. Furthermore, U.S. Pat. No. 4,715,972, issued Dec. 29, 1987 toPacholke, discloses a solid lubricant additive for gear oils comprisingsolid lubricant particles combined with a stabilizing agent and a fluidcarrier, wherein the solid lubricant particles are selected from thegroup consisting of molybdenum disulfide, graphite, cerium fluoride,zinc oxide, tungsten disulfide, mica, boron nitrate, boron nitride,borax, silver sulfate, cadmium iodide, lead iodide, barium fluoride, tinsulfide, fluorinated carbon, PTFE, intercalated graphite, zincphosphide, zinc phosphate, and mixtures thereof. This patent furtherdiscloses that such lubricant additive provides the gear oil withimproved demulsibility, stability and compatibility characteristics ofthe gear oil when contaminated with water.

Polymethacrylic acid esters or polymethacrylates are long chain esterscommonly used in the lubricating oil industry as viscosity indeximprovers (VII). Their molecular masses lie predominantly between 20,000and 500,000. The properties of the homo- or co-polymers of the variousalkylmethacrylates differ with the chain length of the alcohol used tomake the ester and the degree of polymerization. Olefin co-polymers(OCP) are manufactured from ethylene and propylene by means of Zieglercatalysts and are commonly used in the lubricating oil industry as VIIs.Dispersant Olefin Co-polymers (DOCP) are multifunctional VIIs; theviscosity improving effect is combined with dispersant properties by theinclusion of cyclic imides such as N-vinylimidazole and similarfragments in the polymers.

Accordingly, it is an object of the present invention to provide alubricant additive composition having good anti-sticking properties whenused in transmission oils.

SUMMARY OF THE INVENTION

The present invention provides a novel additive composition for atransmission oil comprising:

-   -   a) an oil dispersion of hexagonal boron nitride and;    -   b) a viscosity index improver selected from the group consisting        of:        -   i) a polymethacrylate,        -   ii) a dispersant polymethacrylate, and        -   iii) a dispersant olefin copolymer;        -   wherein the weight ratio of the oil dispersion of hexagonal            boron nitride to the viscosity index improver is in the            range of from about 99:1 to about 1:99.

Typically, the concentration of the oil dispersion of hexagonal boronnitride is from about 1 to about 99 wt %, preferably from about 5 toabout 95 wt % and the concentration of the viscosity index improver isfrom about 1 to about 99 wt %, preferably from about 5 to about 95 wt %,based on the total weight of the additive composition.

The additive composition of the present invention may optionally furthercontain an oil dispersion of hydrated alkali metal borate containing ahydrated alkali metal borate, a dispersant, optionally a detergent, andan oil of lubricating viscosity.

The additive composition of the present invention may be suitablyemployed in both manual transmission gear oils and automatictransmission oils. Preferably, the additive composition will be employedin a manual transmission gear oil.

The present invention further provides a lubricating oil compositioncomprising a major amount of a transmission oil of lubricating viscosityand an effective synchronizer sticking reducing amount of the additivecomposition described above. Preferably, the transmission oil is amanual transmission gear oil.

Among other factors, the present invention is based in part upon thesurprising discovery that the unique combination of an oil dispersion ofhexagonal boron nitride and a certain viscosity index improver selectedfrom a polymethacrylate, dispersant polymethacrylate and a dispersantolefin copolymer, provides a significant and unexpected reduction insynchronizer sticking when used as an additive composition in a manualtransmission gear oil.

DETAILED DESCRIPTION OF THE INVENTION

As noted above, the present invention is directed to a novel additivecomposition for a transmission oil comprising an oil dispersion ofhexagonal boron nitride and a viscosity index improver selected thegroup consisting of:

-   -   a. a polymethacrylate,    -   b. a dispersant polymethacrylate, and    -   c. a dispersant olefin copolymer;        wherein the weight ratio of the oil dispersion of hexagonal        boron nitride to the viscosity index improver is in the range of        from about 99:1 to about 1:99.

Each of the components in the additive composition of the presentinvention will be described in further detail below. Unless otherwisestated, all percentages are in weight percent (wt %).

The Oil Dispersion of Hexagonal Boron Nitride

The additive composition of the present invention contains an oildispersion of hexagonal boron nitride.

Hexagonal boron nitride, or h-BN, is a hexagonal, graphite-like form ofboron nitride, having a layered structure and planar 6-membered rings ofalternating boron and nitrogen atoms. On alternate sheets, boron atomsare directly over nitrogen atoms. Hexagonal boron nitride can beprepared by heating boric oxide, boric acid or boric acid salts withammonium chloride, alkali cyanides or calcium cyanamide at atmosphericpressure. Hexagonal boron nitride may also be prepared by the reactionof boron trichloride or boron trifluoride with ammonia. A discussion ofhexagonal boron nitride can be found, for example, in Kirk-Othmer,Encyclopedia of Chemical Technology, Fourth Edition, Vol. 4, pp.427-429, John Wiley and Sons, New York, 1992.

Generally, the oil dispersion of hexagonal boron nitride will have amean particle size of less than 1 micron. Preferably, the oil dispersionof hexagonal boron nitride will have a particle size distributionwherein 90% or greater of the particles are less than about 0.5 microns(500 nanometers, nm), with a preferred mean particle size of less thanabout 0.3 microns (300 nm).

Typically, the oil dispersion of hexagonal boron nitride will containfrom, about 1 to about 50 wt % of the hexagonal boron nitride solids,preferably from about 1 to about 20 wt %, and more preferably from about5 to about 15 wt %, based on the total weight of the oil dispersion.

Preferably, the oil dispersion of hexagonal boron nitride will contain asurfactant as a stabilizer for the oil dispersion. Typical surfactantsfor use as a stabilizer include ethylene-propylene copolymers, orterpolymers of ethylene, propylene and an unconjugated dienes commonlyknown as ethylene-propylene-diene terpolymer, ethylene-propylenecopolymers grafted with a nitrogen-containing vinyl functionalityselected from the group consisting of N-vinyl pyrrollidone and N-vinylpyridine, and the like. The ethylene-propylene copolymer generally hasan average molecular weight in the range of from about 22,000 to about200,000. A preferred surfactant is ethylene-propylene copolymer whichhas substantially equal proportions of ethylene and propylene monomersand an average molecular weight of from about 22,000 to about 40,000.When present, the surfactant concentration in the oil dispersion ofhexagonal boron nitride will typically range from about 0.1 to about 25wt %, preferably from about 2 to about 7 wt %, and more preferably fromabout 3.0 to about 5.0 wt %, based on the total weight of the oildispersion of hexagonal boron nitride.

The lubricant oil used to prepare the oil dispersion of hexagonal boronnitride may be selected from the same group of natural or syntheticlubricating oils described above for use in preparing the oil dispersionof hydrated alkali metal borate, but other carrier fluids have beenfound to be satisfactory, including vegetable oils such as rapeseed oil;liquid hydrocarbons such as aliphatic and aromatic naphthas and mixturesthereof; synthetic lubricant fluids such as polyalphaolefins,polyglycols, diester fluids, and mixtures of these liquids. Moreover,the oil used in forming the oil dispersion of hexagonal boron nitridemay be the same as, or different from, the lubricant oil employed inpreparing the oil dispersion of hydrated alkali metal borate. Typicaloils for preparing the oil dispersion of hexagonal boron nitride includethe Group I and Group II base oils, such as 150 solvent neutralpetroleum oil.

In general, the oil dispersion of hexagonal boron nitride is present inthe additive composition of the present invention in the range of fromabout 1 to about 99 wt %, preferably from about 5 to about 95 wt %, andmore preferably from about 10 to about 90 wt %, based on the totalamount of the additive composition.

Viscosity Index Improver (VI Improver)

The additive composition of the present invention contains apolymethacrylate, dispersant polymethacrylate or a dispersant olefincopolymer VI improver.

A. The Polymethacrylate (PMA) or Dispersant Polymethacrylate

Typically, the polymethacrylate VI improvers employed in the presentinvention are polymeric methacrylates containing short, intermediate,and long-chain hydrocarbon side chains. Short-chain hydrocarbon sidechains typically have from about 1 to about 7 carbon atoms. For example,both methyl and butyl (either n-butyl, isobutyl, or mixtures of the two)methacrylates have been used. Methyl methacrylate is the most common.Intermediate-chain hydrocarbon side chains typically contain from about8 to about 15 carbon atoms and may be derived from alcohols including2-ethylhexyl alcohol, isodecyl alcohol and alcohol mixtures which maybe, for example, C₈ to C₁₀, C₁₂ to C₁₄ or C₁₂ to C₁₅ alcohol mixtures.Long-chain hydrocarbon side chains generally will contain about 14 ormore carbon atoms and may be based, for example, on C₁₆ to C₁₈ or C₁₆ toC₂₀ alcohol mixtures.

The polymethacrylate VI improvers which may be employed in the presentinvention are any type of non-dispersant type or dispersant typepolymethacrylate compounds which are used as VI improvers for alubricating oil.

The non-dispersant type polymethacrylate VI improvers may be a polymerof a compound represented by the formula:

CH₂═C(CH₃)—CO₂—R¹

In formula (1) R¹ is a straight chain or branched alkyl group such asmethyl, ethyl, propyl, butyl, hexyl, heptyl, octyl, nonyl, decyl,undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl,heptadecyl, and octadecyl groups.

Dispersancy may be incorporated into the PMA with an appropriate polarmonomer by any number a methods known by the skilled artisan such ascopolymerization, graft polymerization or post reaction of a reactivespecies into or onto the polymer. Typically, such methods involve theincorporation of a polar group derived from nitrogen or oxygen.Nitrogen-based groups are derived from amines, for example,polyalkyleneamines such as diethylenetriamine and triethylenetetramine.Oxygen-based groups are alcohol-derived such as hydroxyethylmethacrylates or ether-containing methacrylates. Although nitrogen-basedPMAs are exemplified in the present invention, oxygen-based PMAs arealso contemplated within the scope of the present invention. Examples ofoxygen-based PMAs are those derived from polyhydric alcohols such asglycols, trivalent alcohols such as glyercol and higher alcohols, suchas erythrytol, pentaerythrytol, mannitol and the like. Moreover,ether-containing PMAs are also well known in the art. Further details ofoxygen-based PMAs may be found, for example, in U.S. Pat. Nos. 3,249,545and 3,052,648, the disclosures which is hereby incorporated for allpurposes.

Specific examples of the dispersant polymethacrylate VI improvers arecopolymers obtained by copolymerizing one or more monomers selected fromcompounds represented by formula (1) with one or morenitrogen-containing monomers selected from compounds represented byformulas (2) and (3)

CH₂═C(R²)CO₂—R³—X¹  Formula 2

CH₂═C(R⁴)—X²  Formula 3

In formulas (2) and (3) R² and R⁴ are each independently hydrogen ormethyl, R³ is a straight chain or branched alkylene group having fromabout 1 to about 18 carbon atoms, such as ethylene, propylene, butylene,pentylene, hexylene, heptylene, octylene, nonylene, decylene,undecylene, dodecylene, tridecylene, tetradecylene, pentadecylene,hexadecylene, heptadecylene, and octadecylene groups, X¹ and X² eachindependently an amino- or heterocyclic-residue having about 1 or about2 nitrogen atoms and 0 to about 2 oxygen atoms. Specific examples of X¹and X² are dimethylamino, diethylamino, dipropylamino, dibutylamino,anilino, toluidino, xylidino, acetylamino, benzoilamino, morpholino,pyrolyl, pyridyl, methylpyridyl, pyrrolidinyl, piperidinyl, quinonyl,pyrrolidonyl, pyrrolidono, imidazolino, and pyrazino groups.

Specific examples of the nitrogen-containing monomers represented byformula (2) or (3) are dimethylaminomethylmethacrylate,diethylaminomethylmethacrylate, dimethylaminoethylmethacrylate,diethylaminoethylmethacrylate, 2-methyl-5-vinylpyridine,morpholinomethylmethacrylate, morpholinoethylmethacrylate,N-vinylpyrrolidone, and mixtures thereof.

A particularly beneficial PMA employed in the present invention is anester polymer, having principally from about 1 to about 20, preferablyfrom about 8 to about 14, carbon atoms. It can be prepared by apolymerization reaction with a basic monomer and a peroxide or azoicinitiator in a hydrocarbon solvent such as toluene or a mineral orsynthetic base oil. The basic monomers used to prepare the PMA areprincipally monocarboxylic acid esters such as methacrylate, acrylate,crotonate, tiglicate, and angelicate. The PMA may also be prepared byreaction with olefinic copolymers (i.e., ethylene-propylene copolymer)in oil.

The average molecular weight of the PMA will be in the range of fromabout 20,000 to about 500,000. Preferably, the molecular weight willrange from about 50,000 to about 300,000 and more preferably, from about80,000 to about 150,000.

A further discussion of PMA VI improvers and dispersant PMA VI improverscan be found, for example, in “Lubricant Additives Chemistry andApplications”, Leslie R. Rudnick, Editor, Chapters 5 and 11, MarcelDekker, Inc, New York 2003 and U.S. Pat. No. 6,642,189.

B. Dispersant Olefin Copolymer (OCP)

The dispersant OCPs employable in the present invention includecopolymers of two or more olefins such as ethylene, propylene, butylene,iso-butylene, isoprene, butadiene and the like, as well as copolymers ofthese olefins with other monomers such as styrene, cyclopentadiene,dicyclopentadiene, ethylidene-norbornene and so on.

Exemplary dispersant OCPs for the purpose of the present inventionrelate to ethylene copolymers. Oil soluble ethylene copolymers used inthe invention generally will have a number-average molecular weight(M_(n)) of from above about 5,000 to about 500,000; preferably fromabout 10,000 to about 200,000 and optimally from about 20,000 to about100,000. They will generally have a narrow range of molecular weight, asdetermined by the ratio of weight-average molecular weight (M_(w)) tonumber average molecular weight (M_(n)). Polymers having a M_(w)/M_(n)of less than 10, preferably less than 7, and more preferably 4 or lessare most desirable. As used herein and (M_(n)) and (M_(w)) are measuredby the well known techniques of vapor phase osmometry (VPO), membraneosmometry and gel permeation chromatography. In general, polymers havinga narrow range of molecular weight may be obtained by a choice ofsynthesis conditions such as choice of principal catalyst and cocatalystcombination, addition of hydrogen during the synthesis, etc. Postsynthesis treatment such as extrusion at elevated temperature and underhigh shear through small orifices, mastication under elevatedtemperatures, thermal degradation, fractional precipitation fromsolution, etc. may also be used to obtain narrow ranges of desiredmolecular weights and to break down higher molecular weight polymer todifferent molecular weight grades for VI use.

These polymers are prepared from ethylene and ethylenically unsaturatedhydrocarbons including cyclic, alicyclic and acyclic, containing fromabout 3 to about 28 carbons, e.g. about 2 to about 18 carbons. Theseethylene copolymers may contain from about 15 to about 90 wt. %ethylene, preferably from about 30 to about 80 wt. % of ethylene andfrom about 10 to about 85 wt. %, preferably from about 20 to about 70wt. % of one or more C₃ to C₂₈, preferably C₃ to C₁₈, more preferably C₃to C₈, alpha olefins. While not essential, such copolymers preferablyhave a degree of crystallinity of less than 25 wt. %, as determined byX-ray and differential scanning calorimetry. Copolymers of ethylene andpropylene are most preferred. Other alpha-olefins suitable in place ofpropylene to form the copolymer, or to be used in combination withethylene and propylene to form a terpolymer, tetrapolymer, etc., include1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene,etc.; also branched chain alpha-olefins, such as 4-methyl-1-pentene,4-methyl-1-hexene, 4,4-dimethyl-1-pentene, and 6-methylheptene-1, etc.,and mixtures thereof.

The term copolymer as used herein, unless otherwise indicated, includesterpolymers, tetrapolymers, etc., of ethylene, said C₃ to C₂₈alpha-olefin and/or a non-conjugated diolefin or mixtures of suchdiolefins which may also be used. The amount of the non-conjugateddiolefin will generally range from about 0.5 to about 20 mole percent,preferably from about 1 to about 7 mole percent, based on the totalamount of ethylene and alpha-olefin present.

Representative examples of non-conjugated dienes that may be used as thethird monomer in the terpolymer include:

a. Straight chain acyclic dienes such as: 1,4-hexadiene; 1,5-heptadiene;1,6-octadiene.b. Branched chain acyclic dienes such as: 5-methyl-1,4-hexadiene;3,7-dimethyl 1,6-octadiene; 3,7-dimethyl 1,7-octadiene; and the mixedisomers of dihydro-myrcene and dihydro-cymene.c. Single ring alicyclic dimes such as: 1,4-cyclohexadiene;1,5-cyclooctadiene; 1,5-cyclo-dodecadiene; 4-vinylcyclohexene; 1-allyl,4-isopropylidene cyclohexane; 3-allyl-cyclopentene; 4-allyl cyclohexeneand 1-isopropenyl-4-(4-butenyl)cyclohexane.d. Multi-single ring alicyclic dienes such as: 4,4′-dicyclopentenyl and4,4′-dicyclohexenyl dienes.e. Multi-ring alicyclic fused and bridged ring dienes such as:tetrahydroindene; methyl tetrahydroindene; dicyclopentadiene; bicyclo(2.2.1)-hepta 2,5-diene; alkyl, alkenyl, alkylidene, cycloalkenyl andcycloalkylidene norbornenes such as: ethyl norbornene;5-methylene-6-methyl-2-norbornene;5-methylene-6,6-dimethyl-2-norbornene; 5-propenyl-2-norbornene;5-(3-cyclopentenyl)-2-norbornene and 5-cyclohexylidene-2-norbornene;norbornadiene; etc.

A compound containing at least one ethylenic bond and at least one,preferably two, carboxylic acid groups, or an anhydride group, or apolar group which is convertible into said carboxyl groups by oxidationor hydrolysis may be grafted on the ethylene coploymer. Preferred acidmaterials are (i) monounsaturated C₄ to C₁₀ dicarboxylic acid wherein(a) the carboxyl groups are vicinyl, i.e., located on adjacent carbonatoms, and (b) at least one, preferably both, of said adjacent carbonatoms are part of said mono unsaturation; or (ii) derivatives of (i)such as anhydrides or C₁ to C₅ alcohol derived mono- or diesters of (i).Upon reaction with the ethylene-alpha-olefin copolymer, themonounsaturation of the dicarboxylic acid, anhydride, or ester becomessaturated. Thus, for example, maleic anhydride becomes a hydrocarbylsubstituted succinic anhydride.

Maleic anhydride or a derivative thereof is preferred as it does notappear to homopolymerize appreciably but grafts onto the ethylenecopolymer to give two carboxylic acid functionalities. Such preferredmaterials have the generic formula

wherein R⁵ and R⁶ are the same or different and are hydrogen or ahalogen. Suitable examples additionally include chloro-maleic anhydride,itaconic anhydride, or the corresponding dicarboxylic acids, such asmaleic acid or fumaric acid or their monoesters, etc.

As taught by U.S. Pat. No. 4,160,739 and U.S. Pat. No. 4,161,452, bothof which are incorporated herein by reference, various unsaturatedcomonomers may be grafted on the ethylene copolymer together with theunsaturated acid component, e.g. maleic anhydride. Such graft monomersystems may comprise one or a mixture of comonomers different from theunsaturated acid component and which contain only one copolymerizabledouble bond and are copolymerizable with said unsaturated acidcomponent. Typically, such comonomers do not contain free carboxylicacid groups and are esters containing alpha, beta-ethylenic unsaturationin the acid or alcohol portion; hydrocarbons, both aliphatic andaromatic, containing alpha, beta-ethylenic unsaturation, such as the C₄to C₁₂ alpha olefins, for example isobutylene, hexene, nonene, dodecene,etc.; styrenes, for example styrene, alpha-methyl styrene, p-methylstyrene, p-sec. butyl styrene, etc.; and vinyl monomers, for examplevinyl acetate, vinyl chloride, vinyl ketones such as methyl and ethylvinyl ketone, etc. Comonomers containing functional groups which maycause crosslinking, gelation or other interfering reactions should beavoided, although minor amounts of such comonomers (up to about 10% byweight of the comonomer system) often can be tolerated.

Specific useful copolymerizable comonomers include the following:

(A) Esters of saturated acids and unsaturated alcohols wherein thesaturated acids may be monobasic or polybasic acids containing up toabout 40 carbon atoms such as the following: acetic, propionic, butyric,valeric, caproic, stearic, oxalic, malonic, succinic, glutaric, adipic,pimelic, suberic, azelaic, sebacic, phthalic, isophthalic, terephthalic,hemimellitic, trimellitic, trimesic and the like, including mixtures.The unsaturated alcohols may be monohydroxy or polyhydroxy alcohols andmay contain up to about 40 carbon atoms, such as the following: allyl,methallyl, crotyl, 1-chloroallyl, 2-chloroallyl, cinnamyl, vinyl, methylvinyl, 1-phenallyl, butenyl, propargyl, 1-cyclohexene-3-ol, oleyl, andthe like, including mixtures.(B) Esters of unsaturated monocarboxylic acids containing up to about 12carbon atoms such as acrylic, methacrylic and crotonic acid, and anesterifying agent containing up to about 50 carbon atoms, selected fromsaturated alcohols and alcohol epoxides. The saturated alcohols maypreferably contain up to about 40 carbon atoms and include monohydroxycompounds such as: methanol, ethanol, propanol, butanol, 2-ethylhexanol,octanol, dodecanol, cyclohexanol, cyclopentanol, neopentyl alcohol, andbenzyl alcohol; and alcohol ethers such as the monomethyl or monobutylethers of ethylene or propylene glycol, and the like, includingmixtures. The alcohol epoxides include fatty alcohol epoxides, glycidol,and various derivatives of alkylene oxides, epichlorohydrin, and thelike, including mixtures.

The components of the graft copolymerizable system are used in a ratioof unsaturated acid monomer component to comonomer component of about1:4 to about 4:1, preferably about 1.2 to about 2:1 by weight.

Further dispersant functionality may be incorporated into the OCP byreacting with polyamine or polyol, high functionality long chainhydrocarbyl dicarboxylic acid materials having a functionality of fromabout 1.2 to about 2 and short chain hydrocarbyl substituteddicarboxylic acids, as described, for example, in U.S. Pat. No.5,035,821, which is hereby incorporated for all purposes.

Among the copolymers preferred are ethylene-propylene copolymers (theratio of ethylene:propylene is preferably about 3:1 to about 1:3), andstyrene-isoprene copolymers. Olefin copolymers are manufactured fromethylene and propylene by means of Ziegler catalysts. The molecularweight of olefinic copolymers may vary widely, but preferred copolymerare those having a molecular weight of from about 30,000 to about200,000, more preferably from about 40,000 to about 150,000.

Such preferred copolymers include nitrogen atom-containing polymers, forexample, those obtained by copolymerizing or grafting, with an acidiccomponent such as maleic acid or anhydride thereof, onto an olefiniccopolymer, followed by forming amide or imide linkages by reaction withpolyamines.

Another such preferred copolymer is that obtained by oxidizing anolefinic copolymer, followed by reacting the oxidized polymer withpolyamines. Still another copolymer is that obtained by oxidizing anolefinic copolymer followed by Mannich condensation with formaldehydeand polyamines.

Another preferred copolymer is that obtained by copolymerizing olefinswith a nitrogen atom-containing monomer, or grafting a nitrogenatom-containing monomer onto an olefinic copolymer such asN-vinylpyrrolidone, N-vinylthiopyrrolidone, a dialkylaminoethylmethacrylate or the like (the content of nitrogen atom-containingmonomer preferably being from about 0.1 to about 10 wt %).

In general, the VI Improver is present in the additive composition ofthe present invention in the range of from about 1 to about 99 wt %,preferably from about 5 to about 95 wt %, and more preferably from about10 to about 90 wt %, based on the total weight of the additivecomposition.

A further discussion of dispersant OCP VI improvers can be found, forexample, in “Lubricant Additives; Chemistry and Applications”, Leslie R.Rudnick, Editor, Chapters 5 and 10, Marcel Dekker, Inc, New York 2003.

The Hydrated Alkali Metal Borate

The additive composition of the present invention may optionally furthercontain an oil dispersion of hydrated alkali metal borate as describedbelow.

Hydrated alkali metal borates are well known in the art. Representativepatents disclosing suitable borates and methods of manufacture include:U.S. Pat. Nos. 3,313,727; 3,819,521; 3,853,772; 3,912,643; 3,997,454;and 4,089,790.¹⁻⁶

The hydrated alkali metal borates suitable for use in the presentinvention can be represented by the following general formula:

M₂O.xB₂O₃ .yH₂O

wherein M is an alkali metal, preferably sodium or potassium; x is anumber from about 2.5 to about 4.5 (both whole and fractional); and y isa number from about 1.0 to about 4.8. More preferred are the hydratedpotassium borates, particularly the hydrated potassium triborates. Thehydrated borate particles will generally have a mean particle size ofless than 1 micron.

In the alkali metal borates employed in this invention, the ratio ofboron to alkali metal will preferably range from about 2.5:1 to about4.5:1.

Oil dispersions of hydrated alkali metal borates are generally preparedby forming, in deionized water, a solution of alkali metal hydroxide andboric acid, optionally in the presence of a small amount of thecorresponding alkali metal carbonate. The solution is then added to alubricant composition comprising an oil of lubricating viscosity, adispersant and any optional additives to be included therein (e.g., adetergent, or other optional additives) to form an emulsion that is thendehydrated.

Because of their retention of hydroxyl groups on the borate complex,these complexes are referred to as “hydrated alkali metal borates” andcompositions containing oil/water emulsions of these hydrated alkalimetal borates are referred to as “oil dispersions of hydrated alkalimetal borates”.

Preferred oil dispersions of alkali metal borates will have a boron toalkali metal ratio of from about 2.5:1 to about 4.5:1. In anotherpreferred embodiment, the hydrated alkali metal borate particlesgenerally will have a mean particle size of less than 1 micron. In thisregard, it has been found that the hydrated alkali metal boratesemployed in this invention preferably will have a particle size where90% or greater of the particles are less than 0.6 microns.

In the oil dispersion of hydrated alkali metal borate, the hydratedalkali metal borate will generally comprise from about 10 to about 75 wt%, preferably from about 25 to about 50 wt %, more preferably from about30 to about 40 wt % of the total weight of the oil dispersion ofhydrated borate.

In general, when employed, the oil dispersion of hydrated alkali metalborate is present in the additive composition of the invention in therange of from about 10 to about 90 wt %, based on the total weight ofthe additive composition.

The additive compositions and lubricant compositions of the presentinvention can further employ surfactants, detergents, other dispersantsand other conditions as described below and known to those skilled inthe art. Optionally, the additive compositions may contain analkylaromatic or polyisobutenyl sulfonate.

The oil dispersions of hydrated alkali metal borates employed in thisinvention generally comprise a dispersant, an oil of lubricatingviscosity, and optionally a detergent, that are further detailed below.

The dispersant employed in the oil dispersion of hydrated alkali metalborate optionally employable in the present invention can be ashlessdispersants such as an alkenyl succinimide, an alkenyl succinicanhydride, an alkenyl succinate ester, and the like, or mixtures of suchdispersants.

Ashless dispersants are broadly divided into several groups. One suchgroup is directed to copolymers which contain a carboxylate ester withone or more additional polar function, including amine, amide, imine,imide, hydroxyl carboxyl, and the like. These products can be preparedby copolymerization of long chain alkyl acrylates or methacrylates withmonomers of the above function. Such groups include alkylmethacrylate-vinyl pyrrolidinone copolymers, alkylmethacrylate-dialkylaminoethyl methacrylate copolymers and the like.Additionally, high molecular weight amides and polyamides or esters andpolyesters such as tetraethylene pentamine, polyvinyl polysterarates andother polystearamides may be employed. Preferred dispersants areN-substituted long chain alkenyl succinimides.

Alkenyl succinimides are usually derived from the reaction of alkenylsuccinic acid or anhydride and alkylene polyamines. These compounds aregenerally considered to have the formula

wherein R⁷ is a substantially hydrocarbon radical having a molecularweight from about 400 to about 3,000, that is, R⁷ is a hydrocarbylradical, preferably an alkenyl radical, containing from about 30 toabout 200 carbon atoms; Alk is an alkylene radical of from about 2 toabout 10, preferably from about 2 to about 6, carbon atoms, R⁸, R⁹, andR¹⁰ are selected from a C₁ to C₄ alkyl or alkoxy or hydrogen, preferablyhydrogen, and z is an integer from about 0 to about 10, preferably fromabout 0 to about 3. The actual reaction product of alkylene succinicacid or anhydride and alkylene polyamine will comprise the mixture ofcompounds including succinamic acids and succinimides. However, it iscustomary to designate this reaction product as a succinimide of thedescribed formula, since this will be a principal component of themixture. See, for example, U.S. Pat. Nos. 3,202,678; 3,024,237; and3,172,892.

These N-substituted alkenyl succinimides can be prepared by reactingmaleic anhydride with an olefinic hydrocarbon followed by reacting theresulting alkenyl succinic anhydride with the alkylene polyamine. The R¹radical of the above formula, that is, the alkenyl radical, ispreferably derived from a polymer prepared from an olefin monomercontaining from about 2 to about 5 carbon atoms. Thus, the alkenylradical is obtained by polymerizing an olefin containing from about 2 toabout 5 carbon atoms to form a hydrocarbon having a molecular weightranging from about 400 to about 3,000. Such olefin monomers areexemplified by ethylene, propylene, 1-butene, 2-butene, isobutene, andmixtures thereof.

The preferred polyalkylene amines used to prepare the succinimides areof the formula:

wherein z is an integer of from about 0 to about 10 and Alk, R⁸, R⁹, andR¹⁰ are as defined above.

The alkylene amines include principally methylene amines, ethyleneamines, butylene amines, propylene amines, pentylene amines, hexyleneamines, heptylene amines, octylene amines, other polymethylene aminesand also the cyclic and the higher homologs of such amines as piperazineand amino alkyl-substituted piperazines. They are exemplifiedspecifically by ethylene diamine, triethylene tetraamine, propylenediamine, decamethyl diamine, octamethylene diamine, diheptamethylenetriamine, tripropylene tetraamine, tetraethylene pentamine, trimethylenediamine, pentaethylene hexamine, ditrimethylene triamine,2-heptyl-3-(2-aminopropyl)-imidazoline, 4-methyl imidazoline,N,N-dimethyl-1,3-propane diamine, 1,3-bis(2-aminoethyl)imidazoline,1-(2-aminopropyl)-piperazine, 1,4-bis(2-aminoethyl)piperazine and2-methyl-1-(2-aminobutyl)piperazine, Higher homologs such as areobtained by condensing two or more of the above-illustrated alkyleneamines likewise are useful.

The ethylene amines are especially useful. They are described in somedetail under the heading “Ethylene Amines” in Encyclopedia of ChemicalTechnology, Kirk-Othmer, Vol. 5, pp. 898-905 (Interscience Publishers,New York, 1950).

The term “ethylene amine” is used in a generic sense to denote a classof polyamines conforming for the most part to the structure

H₂N(CH₂CH₂NH)_(a)H

wherein a is an integer from about 1 to about 10.

Thus, it includes, for example, ethylene diamine, diethylene triamine,triethylene tetraamine, tetraethylene pentamine, pentaethylene hexamine,and the like.

Also included within the term “alkenyl succinimides” are post-treatedsuccinimides such as post-treatment processes involving ethylenecarbonate disclosed by Wollenberg, et U.S. Pat. No. 4,612,132;Wollenberg, et al., U.S. Pat. No. 4,746,446; and the like as well asother post-treatment processes each of which are incorporated herein byreference in its entirety.

Preferably, the dispersant component, such as a polyalkylenesuccinimide, comprises from about 2 to about 40 wt %, more preferablyfrom about 5 to about 20 wt %, and even more preferably from about 5 toabout 15 wt %, of the weight of the oil dispersion of hydrated alkalimetal borate.

Polyalkylene succinic anhydrides or a non-nitrogen containing derivativeof the polyalkylene succinic anhydride (such as succinic acids, Group Iand/or Group II mono- or di-metal salts of succinic acids, succininateesters formed by the reaction of a polyalkylene succinic anhydride, acidchloride or other derivative with an alcohol, and the like) are alsosuitable dispersants for use in the compositions of this invention.

The polyalkylene succinic anhydride is preferably a polyisobutenylsuccinic anhydride. In one preferred embodiment, the polyalkylenesuccinic anhydride is a polyisobutenyl succinic anhydride having anumber average molecular weight of at least 500, more preferably atleast about 900 to about 3,000 and still more preferably from at leastabout 900 to about 2,300.

In another preferred embodiment, a mixture of polyalkylene succinicanhydrides is employed. In this embodiment, the mixture preferablycomprises a low molecular weight polyalkylene succinic anhydridecomponent and a high molecular weight polyalkylene succinic anhydridecomponent. More preferably, the low molecular weight component has anumber average molecular weight of from about 500 to below 1,000 and thehigh molecular weight component has a number average molecular weight offrom about 1000 to about 3,000. Still more preferably, both the low andhigh molecular weight components are polyisobutenyl succinic anhydrides.Alternatively, various molecular weights polyalkylene succinic anhydridecomponents can be combined as a dispersant as well as a mixture of theother above referenced dispersants as identified above.

As noted above, the polyalkylene succinic anhydride is the reactionproduct of a polyalkylene (preferably polyisobutene) with maleicanhydride. One can use conventional polyisobutene, or highmethylvinylidene polyisobutene in the preparation of such polyalkylenesuccinic anhydrides. One can use thermal, chlorination, free radical,acid catalyzed, or any other process in this preparation. Examples ofsuitable polyalkylene succinic anhydrides are thermal PIBSA(polyisobutenyl succinic anhydride) described in U.S. Pat. No.3,361,673; chlorination PIBSA described in U.S. Pat. No. 3,172,892; amixture of thermal and chlorination PIBSA described in U.S. Pat. No.3,912,764; high succinic ratio PIBSA described in U.S. Pat. No.4,234,435; PolyPIBSA described in U.S. Pat. Nos. 5,112,507 and5,175,225; high succinic ratio PolyPIBSA described in U.S. Pat. Nos.5,565,528 and 5,616,668; free radical PIBSA described in U.S. Pat. Nos.5,286,799, 5,319,030, and 5,625,004; PIBSA made from highmethylvinylidene polybutene described in U.S. Pat. Nos. 4,152,499,5,137,978, and 5,137,980; high succinic ratio PIBSA made from highmethylvinylidene polybutene described European Patent ApplicationPublication No. EP 355 895; terpolymer PIBSA described in U.S. Pat. No.5,792,729; sulfonic acid PIBSA described in U.S. Pat. No. 5,777,025 andEuropean Patent Application Publication No. EP 542 380; and purifiedPIBSA described in U.S. Pat. No. 5,523,417 and European PatentApplication Publication No. EP 602 863. The disclosures of each of thesedocuments are incorporated herein by reference in their entirety.

Preferably, the polyalkylene succinic anhydride or other dispersantcomponent comprises from about 2 to about 40 wt %, more preferably fromabout 5 to about 20 wt %, and even more preferably from about 5 to about15 wt %, of the weight of the oil dispersion of hydrated alkali metalborate.

Typically, in the oil dispersion of hydrated alkali metal borate, thehydrated alkali metal borate is in a ratio of at least 2:1 relative tothe polyalkylene succinic anhydride or other dispersant, whilepreferably being in the range of 2:1 to about 10:1. In a more preferredembodiment the ratio is at least 5:1. In another preferred embodiment,mixtures as defined above of the polyalkylene succinic anhydrides areemployed.

The oil dispersion of hydrated alkali metal borate which is optionallyemployed in the additive compositions of the present invention mayoptionally contain a detergent. There are a number of materials that aresuitable as detergents for the purpose of this invention. Thesematerials include phenates (high overbased or low overbased), highoverbased phenate stearates, phenolates, salicylates, phosphonates,thiophosphonates and sulfonates and mixtures thereof. Preferably,sulfonates are used, such as high overbased sulfonates, low overbasedsulfonates, or phenoxy sulfonates. In addition the sulfonic acidsthemselves can also be used.

The sulfonate detergent is preferably an alkali or alkaline earth metalsalt of a hydrocarbyl sulfonic acid having from about 15 to about 200carbons. Preferably the term “sulfonate” encompasses the salts ofsulfonic acid derived from petroleum products. Such acids are well knownin the art. They can be obtained by treating petroleum products withsulfuric acid or sulfur trioxide. The acids thus obtained are known aspetroleum sulfonic acids and the salts as petroleum sulfonates. Most ofthe petroleum products which become sulfonated contain anoil-solubilizing hydrocarbon group. Also included within the meaning of“sulfonate” are the salts of sulfonic acids of synthetic alkyl arylcompounds. These acids also are prepared by treating an alkyl arylcompound with sulfuric acid or sulfur trioxide. At least one alkylsubstituent of the aryl ring is an oil-solubilizing group, as discussedabove. The acids thus obtained are known as alkyl aryl sulfonic acidsand the salts as alkyl aryl sulfonates. The sulfonates where the alkylis straight-chain are the well-known linear alkylaryl sulfonates.

The acids obtained by sulfonation are converted to the metal salts byneutralizing with a basic reacting alkali or alkaline earth metalcompound to yield the Group I or Group II metal sulfonates. Generally,the acids are neutralized with an alkali metal base. Alkaline earthmetal salts are obtained from the alkali metal salt by metathesis.Alternatively, the sulfonic acids can be neutralized directly with analkaline earth metal base. The sulfonates can then be overbased,although, for purposes of this invention, overbasing is not necessary.Overbased materials and methods of preparing such materials are wellknown to those skilled in the art. See, for example, LeSuer U.S. Pat.No. 3,496,105, issued Feb. 17, 1970, particularly columns 3 and 4.

The sulfonates are present in the oil dispersion in the form of alkaliand/or alkaline earth metal salts, or mixtures thereof. The alkalimetals include lithium, sodium and potassium. The alkaline earth metalsinclude magnesium, calcium and barium, of which the latter two arepreferred.

Particularly preferred, however, because of their wide availability, aresalts of the petroleum sulfonic acids, particularly the petroleumsulfonic acids which are obtained by sulfonating various hydrocarbonfractions such as lubricating oil fractions and extracts rich inaromatics which are obtained by extracting a hydrocarbon oil with aselective solvent, which extracts may, if desired, be alkylated beforesulfonation by reacting them with olefins or alkyl chlorides by means ofan alkylation catalyst; organic polysulfonic acids such as benzenedisulfonic acid which may or may not be alkylated; and the like.

The preferred salts for use in the present invention are those ofalkylated aromatic sulfonic acids in which the alkyl radical or radicalscontain at least about 8 carbon atoms, for example from about 8 to about22 carbon atoms. Another preferred group of sulfonate starting materialsare the aliphatic-substituted cyclic sulfonic acids in which thealiphatic substituents or substituents contain a total of at least 12carbon atoms, such as the alkyl aryl sulfonic acids, alkylcycloaliphatic sulfonic acids, the alkyl heterocyclic sulfonic acids andaliphatic sulfonic acids in which the aliphatic radical or radicalscontain a total of at least 12 carbon atoms. Specific examples of theseoil-soluble sulfonic acids include petroleum sulfonic acids, mono- andpoly-wax-substituted naphthalene sulfonic acids, substituted sulfonicacids, such as cetyl benzene sulfonic acids, cetyl phenyl sulfonicacids, and the like, aliphatic sulfonic acid, such as paraffin waxsulfonic acids, hydroxy-substituted paraffin wax sulfonic acids, etc.,cycloaliphatic sulfonic acids, petroleum naphthalene sulfonic acids,cetyl cyclopentyl sulfonic acid, mono- and poly-wax-substitutedcyclohexyl sulfonic acids, and the like. The term “petroleum sulfonicacids” is intended to cover all sulfonic acids that are derived directlyfrom petroleum products.

Typical Group II metal sulfonates suitable for use in the presentinvention include the metal sulfonates exemplified as follows: calciumwhite oil benzene sulfonate, barium white oil benzene sulfonate,magnesium white oil benzene sulfonate, calcium dipolypropene benzenesulfonate, barium dipolypropene benzene sulfonate, magnesiumdipolypropene benzene sulfonate, calcium mahogany petroleum sulfonate,barium mahogany petroleum sulfonate, magnesium mahogany petroleumsulfonate, calcium triacontyl sulfonate, magnesium triacontyl sulfonate,calcium lauryl sulfonate, barium lauryl sulfonate, magnesium laurylsulfonate, etc. The concentration of metal sulfonate that may beemployed may vary over a wide range, depending upon the concentration ofalkali metal borate particles. When present, however, the detergentconcentration will generally range from about 0.2 to about 10 wt % andpreferably from about 3 to about 7 wt %, based on the total weight ofthe oil dispersion of hydrated borate. In addition, the compositions ofthis invention may contain a mixture of both a metal sulfonate and anashless dispersant, as described above, where the ratio is a factor ofachieving the proper stability of the oil dispersion of hydrated alkalimetal borate.

The oil of lubricating viscosity used to form the oil dispersions ofhydrated alkali metal borate may be any hydrocarbon-based lubricatingoil or a synthetic base oil stock. Likewise, these lubricating oils canbe added to the oil dispersions and additive compositions containingthem, as described herein, in additional amounts, to form finishedlubricating oil compositions. The hydrocarbon-based lubricating oils maybe derived from synthetic or natural sources and may be paraffinic,naphthenic or aromatic base, or mixtures thereof. The diluent oil can benatural or synthetic, and can be different viscosity grades.

In the oil dispersion of hydrated alkali metal borate, the lubricatingoil typically comprises from about 30 to about 70 wt %, more preferablyfrom about 45 to about 55 wt %, based on the total weight of the oildispersion of hydrated alkali metal borate.

When employed the oil dispersion of hydrated alkali metal borate ispresent in the additive composition of the present invention in therange of from about 1 to about 99 wt %, preferably from about 5 to about95 wt %, based on the total weight of the additive composition.

Formulations

The additive composition of the present invention containing the oildispersion of hexagonal boron nitride and VI improver, and optionally,the oil dispersion of hydrated alkali metal borate, may be blendedfurther with additional additives to form additive packages containingthe present additive compositions. These additive packages typicallycomprise from about 10 to about 80 wt % of the additive composition ofthe present invention described above and from about 90 to about 20 wt %of one or more of conventional additives selected from the groupconsisting of ashless dispersants (0-10 wt %), detergents (0-5 wt %),sulfurized hydrocarbons (0-40 wt %), dialkyl hydrogen phosphates (0-15wt %), zinc dithiophosphates (0-20 wt %), alkyl ammonium phosphatesand/or thio-dithiophosphates (0-20 wt %), phosphites (0 to 10 wt %)fatty acid esters of polyalcohols (0-10 wt %), 2,5-dimercaptothiadiazole(0-5 wt %), benzotriazole (0-5 wt %), dispersed molybdenum disulfide(0-5 wt %), foam inhibitors (0-2 wt %), and imidazolines (0-10 wt %) andthe like wherein each wt % is based on the total weight of the additivecomposition.

Fully formulated finished lubricating oil compositions of this inventioncan be formulated from these additive packages upon further blendingwith an oil of lubricating viscosity. Preferably, the additive packagedescribed above is added to a base oil of lubricating viscosity in anamount of from about 1 to about 40 wt %, preferably from about 2 toabout 20 wt %, to provide for the finished lubricating oil compositionwherein the wt % of the additive package is based on the total weight ofthe lubricating oil composition.

A variety of other additives can be present in lubricating oils of thepresent invention. These additives include antioxidants, rustinhibitors, corrosion inhibitors, extreme pressure agents, antifoamagents, other anti-wear agents, and a variety of other well-knownadditives in the art.

EXAMPLES

The invention will be further illustrated by the following examples,which set forth particularly advantageous embodiments. While theexamples are provided to illustrate the present invention, they are notintended to limit it.

Example 1

The additive composition of the present invention was evaluated in alubricating oil for its anti-sticking properties following a test usingan SAE No. 2 bench, which evaluates transmission fluids duringsynchronization. The friction pairs used in this bench comprised a brasssynchronizer ring and a steel gear cone.

During each cycle of the test, the cone is rotating, at a given speed,then the ring moves along the axis of the cone for its braking until itis blocked. At the end of each cycle, the ring is disengaged.

If sticking occurs, a sticking torque is measured when rotation of thecone is resumed. During the test, the lubricating oil and the metalparts are heated to a temperature between about 60° C. and about 90° C.The contact pressure is about 20 MPa and the initial sliding speed is1.6 m/s.

The anti-sticking coefficient for this test was calculated as follows:

${{Anti}\text{-}{sticking}\mspace{14mu} {coefficient}} = {1 - \frac{( {{{No}.\mspace{14mu} {of}}\mspace{14mu} {cycles}\mspace{14mu} {with}\mspace{14mu} {sticking}} )}{( {{Total}\mspace{14mu} {{No}.\mspace{14mu} {of}}\mspace{14mu} {cycles}\mspace{14mu} {in}\mspace{14mu} {test}} )}}$

Accordingly, an anti-sticking coefficient of 0 indicates the presence ofcone on ring sticking during every cycle of the test. Conversely, ananti-sticking coefficient of 1 indicates no sticking at all was observedover the entire duration of the test. Thus, the higher the anti-stickingcoefficient, up to a maximum of 1, the better the anti-stickingperformance of the lubricating oil.

The test lubricating oil compositions were formulated as follows, allthe oils formulated have the same viscosity (about of 9 cSt):

Lubricant Composition 1

Lubricant composition 1 was prepared containing the following:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 12 wt % of a long chain polymethacrylate VI Improver sold under    the name Viscoplex® 0-113 (available from RohMax Additives GmbH,    Darmstadt, Germany), and-   c) 78 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition 2

Lubricant composition 2 was prepared containing the following:

-   a) 10 wt of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 12 wt % of a dispersant long chain polymethacrylate VI Improver    sold under the name Viscoplex® 0-110 (available from RohMax    Additives GmbH, Darmstadt, Germany), and-   c) 78 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition 3

Lubricant composition 3 was prepared containing the following:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 12 wt % of a short chain polymethacrylate VI Improver sold under    the name Viscoplex® 0-030 (available from RohMax Additives GmbH,    Darmstadt, Germany), and-   c) 78 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition 4

Lubricant composition 4 was prepared containing the following:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 12 wt % of a dispersant ethylene-propylene olefin copolymer VI    Improver with a weight average molecular weight of about 39,000    (Paratone® 8500 available from Chevron Oronite Company, LLC, San    Ramon, Calif.), and-   c) 78 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition 5

Lubricant composition 5 was prepared containing the following:

-   a) 7 wt % of an oil dispersion of hydrated potassium triborate,    wherein the oil dispersion contained about 30 wt % of the hydrated    potassium triborate, dispersed in a 150N neutral oil,-   b) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   c) 12 wt % of a long chain polymethacrylate VI Improver sold under    the name Viscoplex® 0-113 (available from RohMax Additives GmbH,    Darmstadt, Germany), and-   d) 71 wt of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition A (Comparative)

Comparative lubricant composition A was prepared containing thefollowing:

-   a) 7 wt % of an oil dispersion of hydrated potassium triborate,    wherein the oil dispersion contained about 30 wt % of the hydrated    potassium triborate, dispersed in a 150 N neutral oil, and-   b) 93 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition B (Comparative)

Comparative lubricant composition B was prepared containing thefollowing:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contains about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent, and-   b) 90 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition C (Comparative):

Comparative lubricant composition C was prepared containing thefollowing:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 12 wt % of a non-dispersant type ethylene-propylene olefin    copolymer VI Improver with a weight average molecular weight of    about 90,000 (Paratone®8002 available from Chevron Oronite Company,    LLC, San Ramon, Calif.), and-   c) 78 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition D (Comparative):

Comparative lubricant composition D was prepared containing thefollowing:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent,-   b) 0.5 wt % of a polyisobutenyl mono-succinimide, and-   c) 89.5 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

Lubricant Composition E (Comparative):

Comparative lubricant composition E was prepared containing thefollowing:

-   a) 10 wt % of an oil dispersion of hexagonal boron nitride, wherein    the oil dispersion contained about 10 wt % of the hexagonal boron    nitride solids, dispersed in a 150 N neutral oil containing a    stabilizing agent-   b) 0.5 wt % of a polyisobutenyl bis-succinimide, and-   c) 89.5 wt % of a 50/50 mixture of neutral oil (150N plus 600N) and    synthetic polyalphaolefin oil.

TABLE 1 No. of Cycles with Cone on Total No. of Anti-sticking SampleRing Sticking Cycles coefficient Base oil 5000 5000 0 ComparativeComposition A 8100 8100 0 Comparative Composition B 6600 6600 0Comparative Composition C 5700 5700 0 Comparative Composition D 64006400 0 Comparative Composition E 8100 8100 0 Composition 1 500 7100 0.931050 5600 0.81 Composition 2 100 6800 0.99 Composition 3 1200 6850 0.82Composition 4 200 20000 0.99 Composition 5 650 20000 0.97

The above data demonstrates that the additive composition of the presentinvention provides significant anti-sticking performance and shows amarked improvement over the comparative compositions.

From the foregoing description, various modifications and changes in theabove-described invention will occur to those skilled in the art. Allsuch modifications coming within the scope of the appended claims areintended to be included therein.

What is claimed is:
 1. A composition, comprising: a transmission oiladditive containing a) an oil dispersion of hexagonal boron nitridehaving a particle size distribution wherein 90% or greater of theparticles are less than about 0.5 microns; and b) a viscosity indeximprover selected from the group consisting of i) a non-dispersantpolymethacrylate, ii) a dispersant polymethacrylate, and iii) adispersant olefin copolymer. wherein the weight ratio of the oildispersion of hexagonal boron nitride to the viscosity index improver isin the range of about 99:1 to about 1:99.
 2. The composition of claim 1,wherein the weight ratio of the oil dispersion of hexagonal boronnitride to the viscosity index improver is in the range of about 5:95 toabout 95:5.
 3. The composition of claim 1, wherein the oil dispersion ofhexagonal boron nitride contains an oil of lubricating viscosity andabout 1 to about 50 wt % of hexagonal boron nitride solids, based on thetotal weight of the oil dispersion.
 4. The composition of claim 3,wherein the oil dispersion of hexagonal boron nitride further contains asurfactant as a stabilizer.
 5. The composition of claim 1, wherein theoil dispersion of hexagonal boron nitride is present in the transmissionoil additive in the range of about 10 to about 90 wt %, based on thetotal weight of the transmission oil additive.
 6. The composition ofclaim 1 wherein the non-dispersant polymethacrylate contains shortchain, intermediate chain or long chain hydrocarbon side chains.
 7. Thecomposition of claim 1, wherein the dispersant polymethacrylate containsshort chain, intermediate chain or long chain dispersant hydrocarbonside chains.
 8. The composition of claim 1, wherein the dispersantolefin copolymer is a dispersant ethylene-propylene olefin copolymer. 9.The composition of claim 1, wherein the transmission oil additivefurther comprises an oil dispersion of hydrated alkali metal borate. 10.The composition of claim 9, wherein the alkali metal in the hydratedalkali metal borate is sodium or potassium.
 11. The composition of claim10, wherein the alkali metal is potassium.
 12. The composition of claim9, wherein the hydrated alkali metal borate is hydrated potassiumtriborate.
 13. The composition of claim 9, wherein the oil dispersion ofhydrated alkali metal borate contains a hydrated alkali metal borate, adispersant, and an oil of lubricating viscosity.
 14. The composition ofclaim 13, wherein the oil dispersion of hydrated alkali metal boratecontains about 10 to about 75 wt % of the hydrated alkali metal borate,based on the total weight of the oil dispersion.
 15. The composition ofclaim 14, wherein the oil dispersion of hydrated alkali metal boratecontains about 2 to about 40 wt % of the dispersant, based on the totalweight of the oil dispersion.
 16. The composition of claim 15, whereinthe oil dispersion of hydrated alkali metal borate further contains adetergent.
 17. The composition of claim 16, wherein the oil dispersionof hydrated alkali metal borate contains about 0.2 to about 10 wt % ofthe detergent, based on the total weight of the oil dispersion.
 18. Thecomposition of claim 9, wherein the oil dispersion of hydrated alkalimetal borate is present in the transmission oil additive in the range ofabout 10 to about 90 wt %, based on the total weight of the transmissionoil additive.
 19. A lubricating oil composition comprising a majoramount of a transmission oil of lubricating viscosity and an effectivesynchronizer sticking reducing amount of a transmission oil additivecontaining; a) an oil dispersion of hexagonal boron nitride having aparticle size distribution wherein 90% or greater of the particles areless than about 0.5 microns; and b) a viscosity index improver selectedfrom the group consisting of (i) a non-dispersant polymethacrylate, (ii)a dispersant polymethacrylate, and iii) a dispersant olefin copolymer,wherein the weight ratio of the oil dispersion of hexagonal boronnitride to the viscosity index improver is in the range of 99:1 to about1:99.
 20. The composition of claim 19, wherein the weight ratio of theoil dispersion of hexagonal boron nitride to the viscosity indeximprover is in the range of about 5:95 to about 95:5.
 21. Thecomposition of claim 19, wherein the lubricating oil compositioncontains about 1 to about 20 wt % of the transmission oil additive,based on the total weight of the lubricating oil composition.
 22. Thecomposition of claim 19, wherein the transmission oil of lubricatingviscosity is a manual transmission gear oil.